Studie směřující k novému způsoby přípravy C-nukleosidů

New synthesis of C-nucleosides using coupling and metahtesis

A modular approach to aryl-C-ribonucleosides via the allylic substitution and ring-closing metathesis sequence: a stereocontrolled synthesis of all four α-/β- andd-/l-C-nucleoside stereoisomers

Iridium(I)-catalyzed allylation of the enantiopure monoprotected copper(I) alkoxide, generated from (S)-5a, with the enantiopure allylic carbonates (R)-9a,b has been developed as the key step in a new approach to C-nucleoside analogues. The anomeric center was thus constructed via a stereocontrolled formation of the C-O rather than C-C bond with retention of configuration. The resulting bisallyl ethers 15a,b (>= 90% de and >99% cc) were converted into C-ribosides 29a,b via the Ru-catalyzed ring-closing metathesis, followed by a diastereoselective dihydroxylation catalyzed by OsO(4) or RuO(4) and deprotection. Variation of the absolute configuration of the starting segments 5a and 9a,b allowed a stereocontrolled synthesis of all four alpha/beta-D/L-combinations

N-heterocyclic carbene catalyzed C-glycosylation : a concise approach from Stetter reaction

Described herein is the first example of an organocatalytic approach for acylanion addition to the anomeric carbon of 2-nitroglucal using an N-heterocyclic carbene catalyst. Control over the reaction conditions gives β-selective and nitro-eliminated C-glycosides, providing opportunities to produce new classes of C-glycoside